I tried understanding that, this is a validation for email address but i need to know what does this mean @"^(?!.)(""([^""\r\]|\[""\r\])""|" and concat-ed with @"([-a-z0-9!#$%&'+/=?^_`{|}~]|(?)(? denotes the email and concat-ed with @"@[a-z0-9][\w.-][a-z0-9].[a-z][a-z.]*[a-z]$"; denotes after the @ sign in email address but how exactly it is described in this code and can someone explain please.
string validEmailPattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
+ @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
+ @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";